The inventive concept relates generally to electronic memory technologies. More particularly, the inventive concept relates to a memory system incorporating a nonvolatile memory device and a related method of operation.
Semiconductor memory devices can be roughly divided into two categories according to whether they retain stored data when disconnected from power. These categories include volatile memory devices, which lose stored data when disconnected from power, and nonvolatile memory devices, which retain stored data when disconnected from power. Examples of volatile memory devices include static random access memory (SRAM) and dynamic random access memory (DRAM). Examples of nonvolatile memory devices include Mask Read-Only Memory (MROM), Programmable ROM (PROM), Erasable Programmable ROM (EPROM), and Electrically Erasable Programmable ROM (EEPROM).
Flash memory is an especially popular form of EEPROM. Flash memory devices are currently found in a wide variety of devices such as computers, cellular phones, personal digital assistants (PDAs), digital cameras, camcorders, voice recorders, personal media players, handheld personal computers (PCs), gaming machines, facsimile machines, scanners, printers, and so on.
In an effort to provide increased storage capacity, researchers have developed flash memory devices capable of storing multiple bits of data in each memory cell. Such devices are commonly referred to as multi-level-cell (MLC) flash memory devices. One drawback of MLC flash memory devices is that they typically have very strict operating margins. For example, their threshold voltage distributions must be controlled with a high level of accuracy in order to avoid errors. Consequently, researchers are continually seeking ways to improve the accuracy and reliability of MLC flash memory devices.